<div id="editor">
	<p>Example text</p>
</div>

<script>
	function getButtonInfo( button ) {
		switch ( button ) {
			default:
			case CKEDITOR.MOUSE_BUTTON_LEFT:
				return 'left';
			break;

			case CKEDITOR.MOUSE_BUTTON_MIDDLE:
				return 'middle';
			break;

			case CKEDITOR.MOUSE_BUTTON_RIGHT:
				return 'right';
			break;
		}
	}

	CKEDITOR.replace( 'editor', {
		on: {
			instanceReady: function( evt ) {
				evt.editor.editable().on( 'mousedown', function( evt ) {
					console.log( getButtonInfo( CKEDITOR.tools.getMouseButton( evt ) ) );
				} );
			}
		}
	} );
</script>
